Wide angle and fish-eye lenses, as well as low-cost camera optics usually generate a lot of distortions in the image. Lens distortion occurs when the camera lens bends the light in some undesirable way. Two common types of lens distortion are barrel distortion and pincushion distortion. Typically, wide angle lenses tend to suffer from barrel distortion and telephoto lenses from pincushion distortion. FIG. 1 illustrates examples of these distortions. As shown in this figure, barrel distortion 110 makes ordinarily straight lines of a rectilinear object 105 to appear to bend outward from the center of the image. Pincushion distortion 115, on the other hand, makes the lines bend inward toward the center. The distortions may be caused, for example, by lens imperfections or may occur from the geometry of the lens.
Image distortions can be critical for many algorithms especially in the computer vision and three dimensional (3D) compositing fields. Therefore, it is desirable to remove the distortions. There are several algorithms for camera calibration. These algorithms, however, require the use of a calibration grid with feature points whose 3D world coordinates are known. There is, therefore, a need in the art for a technique to remove lens distortions without requiring calibration grid points.